Traffic control system



Oct. 24, 1933. J. B. RADFORD 1,931,851

TRAFFIC CONTROL SYSTEM Filed June 12, 1928 5 Sheets-Sheet 1 //v l E/V 70/? JOHN 590mm? A TTDHNEV Oct. 24, 1933. J. B. RADFORD 1,

TRAFFIC CONTROL SYSTEM Filed June 12, 1928 3 Sheets-Sheet 2 I //v VEN TOR JOHN B. fi am/i'o mvfmw ATTORNEY Oct. 24, 1933.

J. B. RADFORDV TRAFFIC CONTROL SYSTEM Filed June 12, 1928 3 Shee..s--Sheet 3 FIG-6.

INVENTOF Jo/50v B. fiAnrnfib v ATTORNEY Patented Oct. 24, 1933 TRAFFIC CONTROL SYSTEM John B. Radford, Valois, Quebec, Canada, assignor to Westernllectric Company, lncorporated, New York, N. Y., a corporation of New York Application June 12, 1928, Serial No. 284,782, and

' in Canada August 12, 1927 1 Claim.

This invention relates to signaling systems for the control of street trafiic.

Its object is to provide a system for the directing of street traffic which utilizes a single pair 5 of wires to control any number of signal lights,

the time interval of each signal light being individually adjustable.

In accordance with this invention a selector switch is provided for each signal light. This selector switch regulates the time interval between light changes and is individually adjustable to suit the traffic conditions at the point where the signal is located. Any number of selector switches may be controlled from a central point by the same controlling apparatus.

The increasing complexity of the problems involved in the orderly control of'street trafiic has led to the extensive use of electric signals, the

present trend being to use visible signals consist-- ing of three colored lights. The preferred traffic cycle for a traflic lane is to show a green Go light for a convenient time, extinguish it, and show an amber Caution light momentarily, extinguish it and show a red Stop light for a corivenient time, extinguish it and show an amber Caution light momentarily, extinguish it and repeat the cycle. This cycle may be condensed to two operations by showing the Caution light momentarily with the Go signal toward the end of the Go operation and extinguishing both together, the Caution remaining oil until near the end of the Stop operation when the Caution light is shown momentarily with the Stop signal and both extinguished together.

At the present time, the-so-called synchronous system is generally used, in which the signal lamps are lighted through switches, usually of the mercury type, operated by a set of cams rotated by a small induction motor. The motor consists of a copper disc revolving between iron pole pieces excited by a winding connected directly to a 110 volt alternating current circuit; the speed of the motor is regulated by eddy currents induced in the revolving disc by the poles of a permanent magnet. The time during which a signal is lighted is varied by altering the relative positions of the cams, while the time required for a complete cycle of operations is regulated by the speed of the motor. If a number of signals are to be controlled, they are combined into groups, each group being controlled by a relay which is operated by the cams on the motor. This system is objectionable because all the signals in a group operate simultaneously, thus abusy intersection laden with streetcar and bus trafiic may have to operate on the same traflic cycle as a quiet intersection. If separate motors be installed to avoid this trouble, it is difiicult to prevent them from getting out of synchronism with a consequent derangement and crowding of the traific. The trouble could beavoided by the use of synchronous motors, but the cost would be material-.

1y higher.

In the so-called progressive system, a modification of the synchronous system, the colors are reversed to form blocks of such length that traffic entering one end of the block on a green signal will just reachthe other end as the red signal turns to green, and thus the traflic proceeds uninterruptedly. This system assumes that the time required to traverse a block is invariable, and that a trafiic cycle may be'used in which North and South bound traffic and East and West bound traffic pass an intersection in equal periods of time. 1

To avoid the difiiculties inherent in the synchronous and progressive systems, the coordinated system was developed, in which the period of the traflic cycle is the same throughout an area, but is subdivided in different proportions to suit the requirements of certain intersections. For example, an area may have a period of 90 seconds, the intersections with light traffic having say 50 seconds Go and 40 seconds Stop, while an intersection carrying heavy street car trafilc may require 60 seconds (30" and 30 seconds Stop, thus lessening the congestion at the busy intersection, without materially affecting the traffic on the cross streets. To the applicants knowledge, up to thetime of the filing of this application, this system has been installed in only one district of a large city on this continent, and, as the system used requires seven wires from each separate intersection to traffic headquarters, it will be seen that, if a large number of intersections are to be controlled, the system will become unwieldy and the expense enormous.

The signaling system described herein employs only one pair of wires from trafiic headquarters for operating any number of intersections having the same period for a traflic cycle but different timing intervals.

Other features and advantages oi. the invention will appear from the following descriptionand from the claim appended thereto, reference 105 being made to the accompanying drawings in whibh: I V

Fig. 1 is a schematic diagram of a traflic signal system.

Fig. 2 is a circuit diagram of a controller, regu- 110 conductors thereto.

lating switch, traflic signals and associated relays,

with manual and automatic control, local Stop switch and remotely controlled Stop switch.

Fig. 3 is a rotary controller Fig. 4 is a view of the lower contacts of a regu:

lating switch.

Fig. 5 is a view of the upper contacts of the same switch.

Fig. 6 is a side view of the regulating switch.

Similar characters of reference indicate corresponding parts throughout the various views.

The rotary controller shown in Fig. 3 is similar to the controller disclosed in United States Patent 1,472,465 issued October 30, 1923 to O. F. Forsberg and R. M. De Vignier.

On the frame 1, is rotatably mounted a spindle to which is rigidly secured a ratchet wheel 2, and two sets of similar wiper arms 3 and 4, arranged to pass over the two banks of contacts 5, each bank consisting of say 25 contacts. In this specific switch, the wiper arms are so arranged that when one end of the wiper arm is rotated off the last bank contact, the other end comes into engagement with the first bank contact. The wiper arms are also so arranged that when rotated, the contact tips make engagement with a second contact before they are out of engagement with the one from which they are passing, thus holding the circuit closed during the movement.

When the magnet 6 is energized, it attracts the armature 7 forcing the free end of the armature downward against the tension of the spring 8, advancing the pawl 9, which is caused to engage another tooth on the ratchet wheel 2 by the spring 10. The ratchet wheel 2 is held stationary by the detent 11. When the magnet 6 is deenergized, the spring 8 forces the free end of the armature 7 upward until the end of the armature 7 comes into contact with the back stop 12. This movement of the free end of the armature 7 carries the pawl 9 upward, rotating the ratchet wheel 2, and advancing the wipers 3 and 4 into engagement with the next set of contacts. This operation is repeated each time the magnet 6 is energized and deenergized.

For further details of the construction of this switch, reference may be had to the above mentioned patent.

The regulating switchshown in Figs. 4, 5, and 6 is similar to the multiple switch disclosed in United States Patent 1,422,549, issued July 11, 1922 to Augustus J. Eaves.

Referring now to Figs. 4, 5, and 6 two circular flat plates 13 and 14 of suitable insulating material are rigidly fixed together, and support two annular members 1'1 and 18 of suitable insulating material. Mounted within the annular members 17 and 18 are two rotatable disc shaped members, 15 and 16; the disc shaped member 16 being firmly attached to the shaft 19, and the disc shaped member 15 being slidably keyed to the shaft 19, the discs 15 and 16 being held to the plates 13 and 14 by the pressure of the spring 20 due to the nut 21.' The shaft 19 and discs 15 and 16 may be rotated by the knob 22, the degree of rotation being indicated on the dial 23.

Mounted on the annular members 17 and 18 are a plurality of spring contacts 24, the free ends bearing on the rotatable discs 15 and 16 and the fixed ends having suitable means for soldering Two commutator segments 25 and 26, of suitable conducting material are securely'positioned in the disc 15, the upper surface of the commutator segments being flush with the surface of the disc, and each commutator segment spanning slightly less than 180" of arc. A commutator segment 27 of suitable conducting material is similarly positioned on the disc 16, spanning an arc equal to that spanned by one contact, and being placed directly above the end of segment 25 adjacent to segment 26.

Referring now to Fig. 2, in which is shown a circuit diagram of the trafilc control system, contact 28 is made and broken at regular intervals by a master controller (not shown) of any suitable type.

When the master controller closes the contact 28, current will flow from battery 29, through contact 28, and wire 30, winding of magnet 6, wire 30 to battery 29, energizing the magnet, and attracting the armature. When the master controller opens the contact 28, the magnet 6 is deenergized, the armature is forced back and the wipers 3 and 4 advance one contact. This cycle of actions will be repeated at regular intervals under the control of the master controller, stepping the wipers from contact to contact around the bank. When one end of the wiper steps off the last contact, the other end of the wiper steps on to the first contact, so that the action is continuous.

The contact bank of wiper 3 is wired to the contacts mounted on the annulus 17 of the control switch, Fig. 4, and the contact b nk of wiper 4 is wired to the contacts mounted on the annulus 18 of the same control switch.

Under normal conditions, the switch 32 is on contact 33, and switch 36 on contact 37. When the wiper 3 is on the first contact of the bank, a circuit is formed from the commercial supply circuit wire 41, switch 32, contact 33, wire 42, wiper 3, bank contact 1 and wire to switch contact #1, commutator segment 25, wire 43, relay 44, wire 40 to the commercial supply circuit. Relay 44, which may be of any suitable type, operates closing a circuit from wire 41, switch 32, contact 33, contacts of relay 44 to signals 50 and wire 40, also to signals 53, wire 56, switch 36, contact 37, wire 57 and wire 40, lighting signals 50 and 53. The signals 50 may be, for example, the Stop signals for North and South traffic and the signals 53 the Go" signals for East and West trafllc. Relay 44 will remain operated and signals 50 and 53 will remain lighted while the wiper 3 steps from bank contact #1 to bank contact #116, when the commutator segment 25 is in the position shown in Fig. 5, and, if the master controller operates once every 4 seconds, these signals will be operated for 16 4=64 seconds.

When wiper 4 steps on to bank contact #16, a circuit is formed from wire 41, switch 32, contact 33, wire 42, wiper 4, bank contact #16 and wire to switch contact #16 commutator segment 27, wire 47, relay 48, to wire 40. Relay 48 will operate and close a path from wire 41, switch 32, contact 33, contacts .of relay 48, signals 54, and 55, wire 56, switch 36, contact 37, wire 57 to wire 40, lighting the signals 54 and 55. Signals 54 may be, for example, "Caution" signals for North and South traflic and signals 55, Caution signals for East and West trafllc. Y

-When wiper 4 steps of! bank contact #16, relay 48 releases, and signals 54 and 55 are extinguished. Similarly, when wiper 3 steps of! bank contact #16, relay 44 releases, and signals 50 and 53 are extinguished.

When wiper 3 steps on to bank contact #17, a circuit is formed from wire 41, switch 32, contact 33, wire 42, wiper 3, bank contact #17 and wiring to switch contact #17, commutator segment 26, wire 45, relay 46 to wire 40, operating relay 46. The operation of relay 46, closes a path from wire 41, switch 32, contact33, contacts of relay 46 to signals 51 and wire 40, also to signals 52, wire 56, switch 36, contact 37, wire 57 to wire 40, lighting signals 51 and 52. The signals 52 may be, for example, the Go signals for North and South traffic and signals 51 the Stop'signals for East and West traific. Relay 46 will remain operated and signals 51 and 52 will remain lighted while the wiper 3 steps from bank contact #17 to bank contact #25, and, if the master controller operates once every'4 seconds, these signals will be operated for 9 4=36 seconds.

When wiper 4 steps on to bank contact #25, a circuit is formed from wire 41, switch 32, contact 33, wire 42, wiper 4, bank contact #25,'and wiring to switch terminal #25, connector 49, wire 47, relay 48 to wire 40, operating relay 48 and lighting the Caution" signals through the circuit previously traced.

Thus one rotation of the rotary controller has resulted in traffic passing North and South for 64 seconds, the last f which showed a Cau tion light, then the-trafiic passes East and West for 36 seconds, the last 4 of which also showed a Caution signal, and this sequence of events will continue as long as the rotary controller is stepped around.

It is obvious, that if the regulating switch be rotated until the end of commutator segment 25 is under a switch contact other than #16, that a difierent subdivision of the total time will result. For example, if the end of commutator segment 25 be under switch contact #14, trafiic will pass from North to South for 56 seconds, and from East'to West for 44 seconds; Furthermore, it is not essential that the regulating switches of different rotary controllers on the same circuit have the same setting, thus one intersection may have say 64 seconds Go and 36 seconds Stop for North and South traffic, and another intersection on the same circuit may have 56 seconds Go and 44 seconds Stop, or other values desired. Furthermore, by varying the number of contacts used on the bank of the rotary controller, and regulating switch, and by varying the timing of the master controller, the timing intervals may be varied over wide limits. Also, on intersections working on a fixed traffic cycle, the regulating switch may take the form. of two conductors, either movable or fired, arranged to short circuit the bank of the rotary controller in two groups.

If abnormal conditions arise at an intersection which render it necessary for a trafiic ofiicer to stop all traflic, switch 36 may be operated to close contacts 38 and 39. The opening of contact 37 cuts off signals 52, 53, 54 and 55, while the closing of contacts 38 and 39 will light signals and 51, stopping all trafiic.

The traflic ofiicer may desire to manually take over the operation of the signals till the-trouble has been cleared. By operating switch 32 to contact 34, and restoring switch 36 to contact 37, the trams officercan control the signals-manually by means of switch 58. contact 59, a circuit may be traced from wire 41, switch 32, contact and wire 34, contact and wire 59, signal 50 to wire 40, and signal 53, wire 56.,

to wire 40, lighting the signals and allowing traific to passsay from North to South. When switch .58 is moved to contact 60, signals 50 and 53 are extinguished and Caution signals 54 and 55 are lighted. When the switch 56 is moved to contact" With switch 58 on.

61, the signals 51 and 52 are lighted, allowing traflic to pass say from East to West. Thu the traflic ofiicer can operate the signals as long as required. As soon as switch 32 is restored to contact 33, the signals operate under control of the master controller and in synchronism with the other signals in the area.

In many cases it is necessary for the Fire Department to have means for stopping all traffic along a predetermined route from the fire station, to permit the fire fighting apparatus to proceed at high speed from the vicinity of the station. A series of intersections are selected to form the desired route, and a relay 63, of any suitable type well known in the art is incorporated in the control circuit of the intersections selected. The wire 57 is opened at points 64 and 65 and connected to the break contacts 66 of the relay 63, and relays 44 and 46 are connected through wires 68 and 69 to the make contacts v 67 of the relay 63, as shown in Fig. 2. The relay may be operated by any suitable source of electric power, Fig. 2 showing a connection to the control battery 29 through a switch 62, located in the fire station. When the switch 62 is closed relay 63 operates, opening contacts 66 and cutting off the return circuit of signals 52, 53, 54 and 55, which may be the Go and Caution signals, and closing contacts 67, placing a short circuit on wires 43 and 45.

The operation of relay 63 has not interfered with the regular operation of the control circuit 28, which continues to step the wipers 3 and 4 round the contact bank. With the control segments 25 and 26 in the position shown in Fig. 2 when wiper 3 is stepping over bank contacts #i to #16 a circuit is made from wire 41, switch 32, contact 33, wire 42, wiper 3, bank contacts #1 to #16 and wiring to switch contacts, segment 25 wire 43, to relay 44, and also wire 68 relay contacts 67 and wire 69 to relay 46, operating relays 44 and 46 and lighting signals 50 and 51, which may be the Stop signals for all trafiic. When wiper 3 is stepping over bank contacts #17 to #25, a similar circuit may be traced to segment 26 and wire 45 to also operate signals 50 and 5l. Thus all trafiic will be stopped until switch 62 is opened when the signals will again operate under the control of the master controller.

To illustrate the flexibility of this invention, in Fig. 1 is shown a small area of a traffic control system. A central control station 70 is indicated, with a master controller in the form of an impulse transmitter sending electric impulses at regular intervals over the pair of conductors 71 and 72, to a plurality of controllers 73,. 74, 75, 76, 77 and 78 located at the various traflic intersections. These trafiic intersections will normally be street intersections, but in some cases, as shown with controller 78, the traffic intersections may combine more than one street intersection. Controllers 73, 74, 76 and 77 are shown each controlling under one controller as shown with controller 78.

Assume that avenue A base heavy stream of trafilc, which in the area shown, is largely through 50 trafflc, and that the other avenues have a normal density or trafllc. Assuming a trafllc cycle of say 100 seconds, we can allow traflic to pass on avenue A for say 60 seconds, and to cross avenue A for seconds. I The other intersections could be on a traffic cycle of say seconds pass and 50 seconds stop. Thus on avenue D for example traflic will move ahead and across avenue A for 40 seconds, then for 10 seconds traflic will continue on avenue D but will be stored in the block between avenues A and B, while trafllc moves on avenue A, then for 50 seconds all traflic stops on avenue 'D and moves on the cross avenues A, B and C. In

this way,-the normal traflic on avenues B, C and be obvious to those skilled in the art that the invention is not limited to the details shown and described, but that suitable modification to adapt it to diflerent circumstances may be made without departing from the scope of the appended claims.

What is claimed is:

A trafllc control system comprising a signal station, an impulse transmitter for sending out impulses at predetermined intervals, a pair or conductors connecting said impulse transmitter to said signal station, magnetically operated stepping switches located at said signal station and operated by electrical impulses transmitted over said pair of conductors from said impulse trans mitter, manually adjustable rotary switches having a series of contacts thereon coresponding to the contacts on said stepping switch, conductors connecting the contacts on said stepping switch to corresponding contacts on said rotary switch, a plurality of light signals, relays controlling the same, an extra pair of contacts on said rotary switch, means connecting each one of said pair oi! extra contacts to one of said relays, a pair 0! commutator segments insulated from each other mounted on said rotary switch and in engagement with said contacts, and means connected to said segments for rotatihgsaid segments to vary the number of contacts brought into engagement with each of said segments.

JOHN B. RADFORD. 

